Ceph is growing rapidly. As firms deploy Ceph, the technical terms such as
“RADOS”, “RBD,” “RGW” and so forth require corresponding marketing terms
that explain what each component does. The terms in this glossary are
intended to complement the existing technical terminology.

Sometimes more than one term applies to a definition. Generally, the first
term reflects a term consistent with Ceph’s marketing, and secondary terms
reflect either technical terms or legacy ways of referring to Ceph systems.

Ceph Project

The aggregate term for the people, software, mission and infrastructure
of Ceph.

cephx

The Ceph authentication protocol. Cephx operates like Kerberos, but it
has no single point of failure.

Third party cloud provisioning platforms such as OpenStack, CloudStack,
OpenNebula, ProxMox, etc.

Object Storage Device

OSD

A physical or logical storage unit (e.g., LUN).
Sometimes, Ceph users use the
term “OSD” to refer to Ceph OSD Daemon, though the
proper term is “Ceph OSD”.

Ceph OSD Daemon

Ceph OSD Daemons

Ceph OSD

The Ceph OSD software, which interacts with a logical
disk (OSD). Sometimes, Ceph users use the
term “OSD” to refer to “Ceph OSD Daemon”, though the
proper term is “Ceph OSD”.

OSD id

The integer that defines an OSD. It is generated by the monitors as part
of the creation of a new OSD.

OSD fsid

This is a unique identifier used to further improve the uniqueness of an
OSD and it is found in the OSD path in a file called osd_fsid. This
fsid term is used interchangeably with uuid

OSD uuid

Just like the OSD fsid, this is the OSD unique identifer and is used
interchangeably with fsid

bluestore

OSD BlueStore is a new back end for OSD daemons (kraken and newer
versions). Unlike filestore it stores objects directly on the
Ceph block devices without any file system interface.

filestore

A back end for OSD daemons, where a Journal is needed and files are
written to the filesystem.

Ceph Monitor

MON

The Ceph monitor software.

Ceph Manager

MGR

The Ceph manager software, which collects all the state from the whole
cluster in one place.

Ceph Metadata Server

MDS

The Ceph metadata software.

Ceph Clients

Ceph Client

The collection of Ceph components which can access a Ceph Storage
Cluster. These include the Ceph Object Gateway, the Ceph Block Device,
the Ceph Filesystem, and their corresponding libraries, kernel modules,
and FUSEs.

Ceph Kernel Modules

The collection of kernel modules which can be used to interact with the
Ceph System (e.g,. ceph.ko, rbd.ko).

Ceph Client Libraries

The collection of libraries that can be used to interact with components
of the Ceph System.

Ceph Release

Any distinct numbered version of Ceph.

Ceph Point Release

Any ad-hoc release that includes only bug or security fixes.

Ceph Interim Release

Versions of Ceph that have not yet been put through quality assurance
testing, but may contain new features.

Ceph Release Candidate

A major version of Ceph that has undergone initial quality assurance
testing and is ready for beta testers.

Ceph Stable Release

A major version of Ceph where all features from the preceding interim
releases have been put through quality assurance testing successfully.

Ceph Test Framework

Teuthology

The collection of software that performs scripted tests on Ceph.

CRUSH

Controlled Replication Under Scalable Hashing. It is the algorithm
Ceph uses to compute object storage locations.

CRUSH rule

The CRUSH data placement rule that applies to a particular pool(s).

Pool

Pools

Pools are logical partitions for storing objects.

systemd oneshot

A systemd type where a command is defined in ExecStart which will
exit upon completion (it is not intended to daemonize)

LVM tags

Extensible metadata for LVM volumes and groups. It is used to store
Ceph-specific information about devices and its relationship with
OSDs.